The overall purpose of this project is to develop improved statistical techniques for using data from animal carcinogenicity tests conducted at high dose levels to estimate long-term human risk from chemical carcinogens at very low dose levels. Current research efforts have focused on such topics as the evaluation of competing risks and pharmacokinetics in the framework of multistage models for carcinogenesis as well as the question of species-to-species extrapolation. Also the question of model convergence at low doses and the incorporation of background is studied.